SOFTWOOD PROPAGATION

There are 3 main types of cuttings, Softwood, Semi-Hardwood and Hardwood. Softwood cuttings are the easiest.

Why would you propagate?

  • Satisfaction – home propagated plants are always best
  • Cost saving
  • Friends neighbours fellow gardeners can provide an almost infinite source of cuttings and perhaps give you a plant that you can’t buy at a nursery.

Many perennials such as Salvia, Pentas, Heliotrope, Buddleia and Lavender in 2/3 years pass their peak (they become woody) and should be replaced.

 Woody plant

Woody plant

 Young healthy plant

Young healthy plant

So if you take cuttings whilst the plants are young and at their peak you will have a continuing display of quality plants in your garden. It is possible to propagate cuttings in water or with some plants by just dropping the cuttings on the ground, but cuttings grown in suitable medium, e.g. soil, compost etc. will give the best results because they will have a strong nourished root formation. The old adage you can’t choose your parents is not true for your cuttings. Unlike seeds, cuttings result in an exact copy of the parent plant so it is important to carefully select the parent. It should be healthy with no diseases, not under stress and preferably not too old. 

Good hygiene is recommended — use a weak bleach solution or undiluted methylated spirits to clean all work surfaces and instruments to stop fungus and other diseases.

Early morning is the optimum time to take cuttings 8 – 9 am. Speed is also important — the less time between taking the cutting and it getting into the propagating mix the better. But you can’t always do this so put your cuttings in labelled plastic bags with a small amount of water or Magic Mix and put them in the frig crisper or an esky to keep them cool.  

Magic Mix is not really that magic, to a 9 litre bucket or watering can of water add 25mls of Seasol concentrate which is a tonic and 25mls of Powerfeed concentrate which is a fertiliser.

Generally speaking softwood cuttings are best taken September to January, but it is possible all year round if the cutting is flexible new growth. A good test as to whether it is the optimum time to take a softwood cutting of a particular plant is to test the flexibility of the stem. It should bend between 45 – 90 degrees and when released spring back. Hence the name Softwood. 

Using the tip is best; the cuttings should be about 10cm (4”) in length and if possible should have at least 3 nodes. The nodes are where the roots are going to form. If you can’t find a suitable tip cutting make the top of the cutting just above a node, it is preferable that the cutting has no flowers or flower buds, but if it does remove them. Remember to cut straight across at the bottom of a cutting and at an angle if you have to make a top cut. That way you won’t plant it upside down. 

 Flexibility of softwood

Flexibility of softwood

When taking the cutting, cut just below a node. If the cuttings are not being processed immediately make the cut further from the node and cut just below the node when ready to deal with it. Use a sharp cutting tool, if secateurs, shear type not anvil, for a clean cut.  

The next step depends very much on the weather. You need to remove at least the bottom half of the leaves from the cutting. If it is expected to be hot you would remove a few more, up to 2/3 and if the remaining leaves are large cut them in half. This is to avoid too much transpiration and the cutting drying out. It is a compromise however as the plant needs leaves to provide carbohydrates through photosynthesis and thus energy to grow. 

 Prepared softwood tip cutting

Prepared softwood tip cutting

 Cutting showing roots at nodes

Cutting showing roots at nodes

 Non tip cutting

Non tip cutting

Most softwood cuttings contain relatively high levels of auxins (rooting hormones) so generally speaking synthetic rooting hormones are not necessary unless a plant is known to be difficult to propagate. If hormones are used, ensure it is the right concentration for softwood cuttings not more than 3000 parts per million, referred to as the ppm or sometimes expressed as 3gms/ litre. Check the label for this. Hormone powder is a lower cost than gel and easier to use. 

Just shake out a small amount onto a folded piece of paper Remember, synthetic hormones are a chemical so treat with caution, wear gloves, use eye protection and wash carefully any skin that comes in contact with the hormone. 

A natural alternative to rooting hormone is honey or vegemite. Whatever you use keep it in a frig not a freezer between usage. Decant only a small amount each time and discard after the completion of the work session. This avoids contamination. You only need to coat the wounded portion of the cutting. If using powder dampen the wound so that the powder sticks to it. 

If the cuttings have marginal flexibility — less than 45 degrees , Its best to cut a sliver of bark from the bottom 1⁄2 inch (10mm) of the cutting and use hormone/honey to cover the exposed area. Cuttings with this lesser flexibility are really more mature Semi Hardwood cuttings and have less available auxins so it is a good idea to use rooting hormone and remember it will take longer to root. 

To be successful you need to provide your cuttings with adequate air, water, humidity, warmth, structure and sunlight.

Fill a pot with your propagation media the size of the pot depends on the number of cuttings you want to propagate. We use an 8inch squat pot which takes between 10 - 15 cuttings. When we have fewer cuttings we use a smaller 4 inch pot. We would recommend 80% quality commercial propagation media (Debco) mixed with 20% perlite.Perlite is made from volcanic glass and stores air well. Air is vital for root formation, it provides the oxygen roots require to grow, and this growth produces CO2 which is absorbed by the air. The optimum Perlite size is P400 but if you can’t get these smaller particles the P500 will do. When using Perlite it is wise to wear gloves and use a mask.In hot weather it is sometimes a good idea to change this mix to 15% perlite 5% vermiculite. These ratios are approximate. The vermiculite stores water. Saturate your propagation mix before starting. We use the Magic Mix but plain water is OK. 

To make a hole for your cutting use a dibble of suitable diameter — about 30 - 50% greater than the diameter of the cutting and with a flattened bottom. Don’t make the hole deeper than the amount of the cutting you are going to insert as it is important to ensure the cutting reaches the bottom of the hole so it can receive moisture. Firm the mix around the cutting and repeat with further cuttings. Repeat with further cuttings. Tag with plant name and date. 

Spray with water or the Magic Mix solution. 

 Dibbles

Dibbles

 Plastic bag incubator

Plastic bag incubator

At this point you need to incubate your pot of cuttings to provide moisture and humidity and promote root growth. You can make an incubator by bending 2 u shaped wire supports and covering with a translucent plastic bag and frame 

Alternatively for a small pot you can use the top half of a plastic bottle. Either way this ensures high humidity and limits water loss through the leaves. Keep the pots out of direct sunlight and ensure the propagation mix does not dry out. Depending on temperature, average time between watering is 4 – 7 days. 

 Plant ready to pot up

Plant ready to pot up

Once the cuttings develop roots it is time to pot them up into individual containers. To test for root formation apply gentle, repeat gentle, upward pressure to the cutting. If there is resistance roots are forming. You then leave for about another ten days before potting up. During this ten days progressively split the plastic bag and finally remove altogether or take the top off the plastic bottle. 

This helps to toughen up the cuttings. During this time more frequent watering will be necessary. We believe with potting mix you get what you pay for. We use Debco Pot Power Ultimate potting mix and some people think that’s crazy, but we have had some bad results with low cost mixes. Again we use Perlite Add to the Debco about 5% Perlite, here we use the Perlite P500. We normally pot up into 10 cm (4”) diameter plastic pots. If you put your cuttings into a 15cm(6”) or lesser diameter you can carefully tip the media and cuttings out, being careful not to damage your cuttings.  If you used a 20 cm (8”) pot as we do it’s best to use a narrow hand spade or large serving spoon to remove each cutting individually. Either way do not try to remove all the mix from around the roots, this will only damage the roots. 

When you pot up, fill the bottom of the pot with potting mix, lay it on its side and carefully position your now rooted cutting so that it is at the same depth as it was in the propagation mix, then fill with more potting mix. This method allows the roots to be spread more evenly in the potting mix 

Firm up around the cutting knock the pot on the bench to remove air pockets and then water well with the Magic Mix or water; also spray the foliage with Magic Mix to help avoid transplant shock. At first keep these plants in the shade and gradually move them into the right environment for their species, that is sun, part shade , etc. Whenever we have them available we use a square pot. Over time we have found that the root formation in square pots is better than that in round. Often the roots in a round pot circle around the inside of the pot and become tangled. 

This does not appear to be the case with square pots and time has shown us that plants grown in square pots progress faster. This is not of course anything new, that great gardening guru Peter Cundall always said that when putting a plant into the ground dig a square hole not a round one. 

When the roots have filled the pot, whatever type of pot you have used, its time to put them on into 15cm(6”) pots where they will grow to sufficient size to be planted out or on into a suitable container.